Oscillation generation



June 25, 1935.

N. E. LINDENBLAD OSCILLATION GENERATION Filed July 21, 1930 2 Sheets-Sheet l NILS E. LINDENBLAD ATTORNEY June 25, 1935. N. E. LINDENBLAD OSCI'LLATION GENERATI ON 2 Sheets-Sheet 2 Filedduly 21, 1930 INVENITOR NlLS E. LINDENBLAD BY W66 AT' FORNEY Patented June 25, 1935 PATENT OFFICE osomm'rron annexation Nils E. Linder blad, Port Jefferson, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application July 21, 1930, Serial No. 469,364

12 Claims.

This invention relates to the generation of alternating electrical current 'and has for an object the provision of new and useful methods and means for generating extremely high frequency electrical oscillations.

Another principal object of this invention is to provide an ultra short wave length oscillator from which increased useful output energy may be obtained. This object is carried out by arranging a number of small, unit oscillators to-.

gether as a single long unit upon which a standing wave is produced. In this way portions of each half wave section become useful for the production of oscillatory energy; and, due to the relatively large number of useful sections that may be incorporated within a single device, the useful high frequency power output is materially augmented.

Heretofore, high frequency oscillations have been generated with the magnetron type of electron discharge device wherein by the action of a magnetic field, electrons ar caused to travel from a centrally disposed cathode to sections of a split anode, alternately. Electrons hit one section of the anode causing it to lower in instantaneous potential, as a result of which, the electrons, cease flowing thereto and start flowing towards the other anode section until the first mentioned section has again risen in potential. The magnetic fleld lengthens the path of electron travel tothe anode sections, thus varying the frequency of oscillation.

It is found, however, that oscillationsabove a certain limit in frequency cannot be produced with -the ordinary type ofoscillator outlined hereinabove. That isto say, because of capacity effects within the tube, electrons striking the anode sections at high frequencies do not alter its potential sufliciently to slow up electron flow to the respective anode sections. A crude anal! ogy may be drawn between a large block of. lead struck by a flake of snow; the efiect of the flake being negligible in moving the block.

Accordingly, to increase the frequency of cur- 'rents generated by a magnetron type of oscillator is one of the main objects of the present invention. To do so the anode sections are lengthened in a fashion such that the mutual inductance between the sections is increased, and, by virtue of the increased mutual inductance flow of electrons to one section of the anode tends to vary the potential on the other. section of the anode in a direction correct for the generation of high frequency oscillations.

To further assist the generation of extremely high frequency oscillations, it is a further object of this invention to produce standing waves upon the cold electrodes of the device used in producing the oscillations. Adjacent portions of the cold electrode sections will consequently have, 5 at all times, currents flowing in opposite direc tions which, because of the mutual inductance between the sections, as already indicated, gives rise to the necessary potential variations on the sections for the production of oscillations. In 10 this way, also, electrons will need to travel only short distances in portions of each half wave section of the electrodes, thereby facilitating oscillation production.

In order to provide a device of the character 15 so far described, which shall have cold electrodes electrically long, yet occupying physically small space, it is a further object of this invention to form the cold electrodes in a fashion such that nodal portions or the relatively ineffective por- 20 -tionsv of the electrodes are shielded outor folded away, the action portions being formed effectively in the form of a plurality of targets.

Still another object of the present invention is to provide coupling for the cold electrode sec- 25 tions in a fashion such that the tube oscillator will not be overloaded, which overloading causes in many instances, cessation of oscillations. To accomplish this object, according to thepresent invention,anodes are coupled through a fraction- 80 ally looped conductor, preferably one-half wave length long at the desired frequency and, an output circuit is connected symmetrically about a nodal point on the looped conductor so as to include a portion of the loop less than one-half 85 wave length long.

Still further objects of the present invention are to provide for the modulation and directional transmission of the oscillations generated in accordance with the invention hereinbefore out- 40 lined.

Turning to the accompanying drawings which are onlyillustrative of the present invention,

Figure 1 diagrammatically indicates apparatus for producing high frequency oscillations by gencrating on cold electrodes of an electron discharge device, standing waves,

Figure 2 is a modification of Figure '1 wherein the cold electrodes are formed as a plurality of 'targets,

Figure-3 is a sectional view of an oscillator illustrating the manner in which'the coldelectrodes may be folded up in order to provide long tube elements having high mutual inductance and yet occupyin small space, and,

surface, or a cathode of the'heater type. The

cathode is energized by a suitable source 01 energy I. Y

In accordance with the present invention there are placed about the cathode 4 curved cold electrodes 6, 8.shown in cross section, encircling the cathode, and forming an elongated sectionalized anode, sectionalized in a direction parallel with the axis of cathode 4. The anode sections or cold electrodes 6, 8 are made long and placed relatively close together so that at high frequencies there is a material amount of mutual inductance therebetween.

By varying the strength of current supplied from source l through variable resistor l2 to solenoid t4, the magnetic field through which electrons travel from the cathode 4 to the anodes may be varied, as a result of which, the time lag of electrons from cathode 4 to the anodes may be changed in a fashion such that a number of standing waves are set up as shown by the dotted lines l6, l8, which indicate standing potential waves, on the anodes. In other words, by varying the electric field and hence the radial force on the electrons, and by varying the magnetic field and hence the periphical force on the electrons so that the cyclic natural period of the electrons through their orbits will coincide with the natural period of the anode elements at one of their harmonic tuning conditions, standing'waves will be set up on the anode elements.

The anodes should be coupled through a looped ,-conductor 20 preferably one-half wave length long, having 'a voltage nodal point 22 which may be connected through a conductor 24 to a suitable source of anode potential (not shown). Although point 22 is a voltage nodal point, the electrically free ends 26, 28 .of the anodes 6, 8 respectively, will, as shown, always be at a maximum alternating potential. The waves on each section 6, 8 will, ofcourse, be out of phase and the currents on'each section will be out of phase with the potential wave on each section. The currents in adjacent sections will flow in opposite directions thereby tending to increase the voltages induced on the respective sections in correct direction for oscillation generation.

In order not to overload the system and thereby cause cessation of oscillations, the output circuit,

in the form of a transmission line '30 leading to 'a'suitable radiator 32 is coupled symmetrically about the v'oltage nodal point 22 so as to include a section of the looped conductor 20 betweenconnecting point 34, 38 of a length less than one- I half wave length.

Modulationyof the energy supplied to a.radiator azimay. be accomplished by supplying keyed alternating energy through transformer 38 to the solenoid l4 and/or am lified complex voltages through transformer 40 to the anode potential;

and, for simultaneous transmission of both, the

} frequency of oscillations supplied through trans- Jformertl should be beyond the range of frequencies supplied through transformer 40. Modulation could be accomplished, of course, by inserting in-seriesjwith transmission line 3. an electron discharge device, whosecontr'ol electrode o! a parabolic metallic element 42 may be utilized.

If desired parabolically arranged tuned wires may be used instead of metallic element 42 for eflecting a reflector action. In such case one may arrange the tuned wires behind radiator 32 an odd number of quarter wave lengths and preferably one-quarter wave length.

In order to shorten the tube, the cold electrodes may be made as shown in Figure 2 in the form of targets 44 which represent portions of the anodes upon which there are maximum potentials.

The intermediate portions 46 may be simple conductors, preferably looped, in order to economize space. Theinactive portions of the cathode 4 may be shielded by shields 48 either of insulating material or, simply metallic sleeves, which form parallel paths for the cathode energizing energy.

In connection with the cathode, it may be stated that it can be energized with unidirectional or as shown in Figure 2, alternating electrical energy. Rather than apply complex currents to the anodes, simple keyed alternating energy amplified by a suitable amplifier 50 may, of lourse, be algebraically added as shown, to the anode potentials.

Another way' of shortening the tube would be to fold away portions of the anode structure as shown diagrammatically in Figure 3. The anode sections are folded into loops 52 representing portions of the elongated anode sections which have minimum values of potential thereon. The remaining portions 44 are effectively small targets for electrons from the cathodes or filament 4. The portions of the cathode opposite the ineffective portions 52' of the anodes may be shielded by shields 48 of a'type similar to those described in connection with Figure 2. I}

Figure 4 discloses another mannerof energizing an oscillator built in accordance with the present invention. Unidirectional energy is fed across a single impedance preferably in the form of a resistance 60. As shown, the cathode and anode are variably tapped thereacross by suitable taps. The solenoid may also be tapped to the resistance, and, by varying the portion of the resistance includedacross the solenoid leads, the magnetic stress applied to the electrons traveling from the cathode to the anode may be varied. If desired, modulation may be accomplished by keying, by means of a switch 62, the energy supplied to the cathode. However, as already indicated, it is preferred that modulating energy be applied to the mid point of the anode connecting loop together with anode potential.

Having thus described my invention, what I claim is:

1. In an electron discharge device, a cathode, and an elongated anode a plurality of half wave lengths long at the operating frequency sectionalized into elongated sections, the sections of the targets having substantial width, the targets of each section being connected together by wires.

3. In an electron discharge device, a cathode, and an elongated anode a plurality of half wave lengths long at the operating frequency sectionalized into elongated sections, the sections of the anode being relatively close to increase their mutual inductance, and means for applying, to the electrons emitted from the cathode, a magnetic field whereby standing waves are produced on said sections, the standing 'waves on diifer'ent sections being out of phase with respect to each other. 4. In an electron an elongated sectionalized anode,

discharge device, a cathode, each section of y the anode comprising a plurality of targets liaving substantial width connected together by wires,

and means for subjecting 'the electrons emitted from the cathode to,a magnetic field.

5. An electron discharge device oscillator hav ing a cathode, and anodes constructed for the production of standing waves thereon, aconductor coupling the anodes together, means for connecting a source or anode potential to a voltage nodal point on the conductor, and an output circuit connected to the conductor symmetrically about the nodal point and including a section of the conductor less than one-half wave length long between coupling points.

6. In an electron discharge device,a cathode, an anode comprising a plurality of elongated sections each a plurality of half wave lengths long at the operating frequency, said sections being disposed around said cathode but electrically unconnected thereto, a connection between said anode sections, and radiating means coupled to .said connection symmetrically about a nodal point on said connectiom 7. Signalling apparatus having, in combination, an electron emitting cathode, a pair of electron discharge device anodes concentrically disposed around said cathode, a looped conductor coupling the anodes together, a transmission line connected directly to and symmetrically about a voltage nodal point on said conductor, and a source of unidirectional positive potential connected to the conductor at its nodal point.-

8. An electron discharge device oscillator having a cathode, and anodes constructed for the production of standing waves thereon, a conductor coupling the anodes together, a connection between a source of anode potential and a voltage nodal point on the conductor, means coupled to said connection for, modulating the oscillations generated by said oscillatonand an output circuit connected to the conductor symmetrically about the nodal point and including a section of the conductor.

9. In an electron discharge device, a cathode, an anode comprising a plurality of elongated sections each a plurality of half wave lengths long at the operating frequency, said sections being disposed around said cathode, a conductor onehalf wave length long coupling the anodes together, and a transmission line coupled symmetrically about a nodal point on the conductor.

10. In an electron discharge device, a cathode, an anode comprising a plurality of elongated sections each a plurality of half wave lengths long at the operating frequency, said sections being disposed around ,said cathode, aconductor a multiple of one-half wave length at the desired frequency coupling the anodes together, and a transmission line coupled symmetrically about the nodal point on the conductor.

11. In an electron discharge device, a cathode, an elongated sectionalized anode, each section of the anode comprising a plurality of electron receiving portions connected together'in series by wires, and means for subjecting the electrons emitted from the cathode to a magnetic field.

12. In an electron discharge device, a'cathode, an elongated anode a plurality of half wave lengths long at the operating frequency sectionalized into elongated sections, the sections'of the anode being relatively close and non-cylindrical in formation to increase their mutual inductance, and means for applying to the electrons emitted from the cathode a magnetic field, the value of said field and the constants of said circuit being so arranged that the cyclic natural period of the electrons through their orbits will coincide with the natural period of the anode elements at one or their harmonic tuning conditions whereby standing waves will be set up on the anode sectionswhich are out of phase with respect to one another.

R118 R. LINDmIBLAD. 

